Digital photography was used in astronomy long before its use by the general public and had almost completely displaced photographic plates by the early 1980s. Not only are CCDs more sensitive to light than plates, but they have a much more uniform and predictable response. The CCDs used in astronomy are similar to those used by the general public, but are generally monochrome and cooled with liquid nitrogen so as to reduce the noise caused by heat. Many astronomical instruments have arrays of many CCDs, sometimes totaling almost a billion pixels. Nowadays amateur astronomers also commonly use digital cameras, including the use of webcams for speckle imaging or "video astronomy".
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